System for operating electric discharge tubes



Dec. c. MASCIARELLI, 2,455,791

SYSTEM FOR OPERATING ELECTRIC DISCHARGE TUBES Filed Aug. 27, 1946 Patented Dec. 7, 1948 UNITED PATENT OFFICE SY TEM: FORjOPEBATING- ELECTRIC DISCHARGE TUBES- 1 This inventionrelates to systems for operating and regulating electric discharge tube-s having thermionic electrodes and more especially to such systems involving luminous tubes, such as fluorescent tubes, neon tubes and other heatedor thermo switch type: ormanually operated 11:.

means which produce an;in clu ctive kick? on the tube terminals.

Other objects will hereinafter appear in the detailed description of one of many embodiments of, the invention. that hasgiven good results in 1 practice and will be pointed out in the appended claim.

In the accompanyingdrawing, Figure 1 is a diagram of a system for operating-and regulatinga, fluorescent lamp embodying my invention.

Figures 2, 3 and 4: are fragmentarydiagrams of modifications,

In the particular drawingsselected for more fully'disclosing the principles underlying my invention and which are to be considered as illustrativermerely, and not restrictive, 10 represents in the present instance, a fluorescent tube of any suitable typehaving thermionic electrodes of filamentsll, l l A source of alternating-current; I2, is connectedby switch I3, to the transformer 14, which preferably is of the closed-magnetic core type and, in the form shown, has a core consisting of two relatively long legs l5 and two relatively short legs I5 connecting the respective ends thereof.

On the legs 15 is disposed a primary winding havingtwo coils Hi, l6 serially connected by the lead I1, and both terminals 18', T9 of the primary are connected bytheleadslo, 2.! with thepower source through the switch l3 which may be a wall-switch of anyusual type.v Thesecondary.

winding, having two coils 22, 22 serially connected by the lead,23, is disposed on the legs l5, andthe end of each coilthereof is axially spaced from the proximate ends of the respective coils ofthe primaryby asubstantial distance to permit. of relatively large magnetic leakage on loaded external circuit, that is, in the present instance, when thetube is producing light. As

willjater appeanthis space between the ends of the-primary and secondary windingais utilized for themounting of tertiary. windings 30, and- 315, for upplying voltage to the filaments l I and. l I of thetube l0, innsuch maner as to insure quick starting and efiicient-operation of, the tube.

The terminal l9; of; the primary is, connected bylead; 24!; to, terminal 25, of the, secondaryand the terminalifi, tothe latter is connestedhy lead 21; to electrode l l of thevtube. The-electr des] l is, connected by. leads vl8, 29.tothe; terminal. I'8 ofttheprimary; Thus,,it will be seen that; the coils of the primary, thecoi-lsof-thersecondary and thetube araconnecteda in a, closed series ill uitl This; arrangement of the transformer pro,- duces what is, sometimes called an auto-trans ormer he primary; of which: s ts f t e coils I6, l6," andthesecondary, of the=coils-; 22; 22f1p1us said-coilsp-l'fi, [6,. In one-view,- thetransformer -ratio,is,-such=that; when; l10 ;volts are im: pressed upon the terminals l8, l9 of the primary, the voltageideveloped, on open circuit between the, terminals l8 and 26, of, such, auto-transformer= will! be about,241 volts. Another view is thatv to, the. voltage developed. between the secondary terminals 25, 26 onopen circuit, is addedvectorially thevoltage impressedupon the primary; l6; l6; Ineither case, the result .is the same so far as the voltage between the terminals l81 -and 25 isconcerned, and it is tube under- StQOdithELtl I do not limit myself, except'as requiredlby theappendedlclaim, to a transformer of any particular type,--shell type, coretype, non=conductively connected primary and secondary; typeor primary. and secondary seriallyconnected'(autoltransformer) type, but 1 preferthe latter type-because of economy of space and manufacturing cost.

The salient feature ofmy invention is the dis- DOSltiOIlzOf the electrode coils-or tertiary windings 38-, 3;l;on the long legstof the core, respectively; in thespaces between the primary and secondary; coils; and spaced axially from the proximate ends thereof. .Inthe'present instance th distanceebetween-lthe proximate ends or a secondary coil, for: example, coil-22 and a primarycoil on the. same leg 16,. the voltages-being asabove settout, is about one inch, the axial length. of. the electrode coil is about one-half inch; the axial:space between one end of, the electrode: coil ,and the secondary. coil 22 is onequartervof an inch andzthe axial spacebetween theothen end Of iSdld-QIBCbIOdECOil and primary 3; coil iii is about one-quarter of an inch. The electrode coil-s 3d, 3 I are connected in series with the electrodes ll, II, respectively.

It is to be understood, of course, that these constants, as well as all others herein, are not to be considered as in the nature of limitations and are stated only for the purpose of completeness of disclosure of one of the many embodiments of the invention.

In the operation of the system above described, upon the closing of the switch !3 the voltage developed across the terminals 30', 36" of the filament coil 30 is approximately 12 volts and the current through the circuit of the electrode or filament I I is about .5 ampere; and the voltage across the terminals 3|, 3!" of the coil 3| and the current through the electrode H are substantially the same as above stated with respect to coil 36 and its circuit.

These tertiary voltages immediately heat the filaments H and l, l to a temperature where electrons are emitted which serve to ionize the gas in the tube under the pressure of the 240 volts impressed across the tube electrodes between the auto-transformer terminals l8 and 26. This renders the gas conducting and are current flows through the secondary windings 22 and 22' thus inducing a back E. M. F. which is out of phase with the voltage across the secondary induced from the primary. The vector sum of these three voltages, i. e., primary, secondary and back E. M. F. becomes 110 to 118 volts depending upon the condition of the tube.

As these voltages resolve to these steadystate values, the voltage on the tertiary windings decreases to about 4.5 volts because of the decreased flux density in the core at their positions. This decreased flux density is due to the fact that the current in the primary winding is out of phase with the arc current flowing through the secondary legs 22 and 22. Because of this disposition of the tertiary windings, the turns ratio can be established such that under running conditions, the filament voltage will be maintained at a level just sufiicient to supply electron emission equivalent to the arc current. The advantage of this feature is the economical and more efiicient use of the entire filament, and longer tube life, as distinguished from spot cathode operation of conventional type fixtures. -'If .so desired, the coils 38', 3| may be axially movable along the core to vary the voltages developed across the terminals thereof at starting and running.

It has been demonstrated during many months of research with a 40 watt fluorescent tube of the type now in general use, that the maximum luminosity of the tube is established practically one second after the closing of the power switch, and also that the small amperage in the electrode circuits is sufficient to prevent sputtering at the electrodes with the disadvantages attendant thereon, the tubes so tested in my system having been used until exhaustion without evidence of discoloration at the electrodes.

In Figure 2,'I have shown a heat-responsive switch 32 in the circuit of one of the filament coils (30) which may be used if desired to facilitate the starting of the tube, if in periods of excessive humidity the tube is slow in starting. In this case, the thermoswitch, adjusted to maintain the filament circuit closed normally, will open said circuit if the current therein remains at starting value of about .5 ampere for more than a very short period, slightly more than one second, in which event, the breaking of said current will induce in the circuit comprising the serially connected primary coils, the secondary coils and. the tube, a voltage surge suflicient to strike the arc in the tube, whereupon said switch will resume its normal position and the current through the electrode circuit in which it is included will drop to its running value.

In Figures 3 and 4 I have shown modification of my invention wherein the filament coils occupy positions other than that shown in Figure 1.

In Figure 3, the coils 30a, 3la are shown concentric with the secondary coils 22, 22, respectively, each being disposed over the exterior surface of its secondary or interposed between the latter and the core. When so located the voltage developed across the terminals of said filament coils at starting and running will be different, respectively, from voltages so developed when they are positioned as in Figure 1.

In Figure 4, the filament coils 30b and 3Ib are disposed on the core between the upper short leg l5 and the respective upper ends of the secondary coils, and axially spaced from the latter. In this case the starting voltage across the coils 30b and 3lb will be less than the running voltage thereof, and this arrangement is useful in connection with thermionic tubes that are not used for illumination.

Having thus described illustrative embodiments of my invention, without, however, limiting myself thereto, what I claim and desire to secure by Letters Patent is:

In a system for operating and regulating an electric discharge tube having thermionic electrode filaments, a source of alternating current, a transformer providing a closed magnetic core having two relatively long legs and two relatively short legs connecting the respective ends of said long legs, primary and secondary windings each providing a coil disposed on the same long core leg, with the end of each primary coil being spaced axially of a long core leg from the end of each secondary coil, to permit a relatively large magnetic leakage between said long legs, means connecting the coils of said primary and secondary windings and said tube in a closed series circuit, filament energizing windings having their terminals connected to said tube filaments, with each filament winding being disposed on a long core leg in a space between said primary and secondary coils, and means for connecting both terminals of said primary winding to said source, whereupon sufficient voltage is developed by said filament energizing windings to immediately heat said filaments to a temperature where electrons are emitted and ionization of the gas in the tube takes place, at the open circuit voltage between the electrodes as developed by said primary and secondary windings, with the magnetic flux density in a long core leg at the location of each filament energizing winding being such that the voltage developed by such windings and result ing heating current in the filaments is reduced from its initial starting value to a lower value when the tube is ionized and operating with a reduced steadystate voltage across its electrodes, due to the back electromotive force induced by flow of arc current through the secondary winding which is out of phase with the voltage across the secondary induced from the primary, and with the out of phase current in said secondary winding being in full control of the energy output of each filament winding to obtain the desired Number degree of filament heating for operating the tube. 1,977,231 GAMILLO MASCIARELLI. 1,980,534 2,222,485 REFERENCES CITED 5 2,256,242 The following references are of record in the 3 2 122 file of this patent:

UNITED STATES PATENTS Number Name Date 10 Number 1,368,507 Kjekstad Feb. 15, 1921 203,789

Name Date 7 Erickson Oct.16, 1934 Kirsten Nov. 13, 1934 McCarthy Nov. 19, 1940 Edwards Sept. 16, 1941 Boucher -1 July '7, 1942 Fries Dec. 15, 1942 FOREIGN PATENTS Country Date Switzerland July 1, 1939 

